Lateral emission, radial emission, and diffusing output optical fibers are utilized in a variety of light-based surgical procedures including laser interstitial thermal therapy, endovenous laser ablation, endometrial coagulation and ablation, endovenous thermal therapy, and photodynamic therapy. Additional surgical interventions have been proposed using these modified output fibers including ablation, vaporization, and/or coagulation of tissue: including hyperplastic prostate tissue, laryngeal tumors, and atherosclerotic and vulnerable plaques.
Fiber modifications, including additions to optical fiber for altering the axial output, typically utilize scattering elements to produce diffuse energy emission over significant lengths of fiber (distal-termini) in both rigid and flexible designs. Fiber optics based upon scatter are generally very limited in total power handling capacity due to conversion of a significant portion of the photonic energy to thermal energy, and a reliance upon polymer matrices for carrying the scattering centers. These scattering modality outputs are referred, herein, as diffuse or diffusing output emissions.
“Radial emission” has been used to describe fiber output ranging from the standard divergence of a high numerical aperture (NA) and axial output (flat polished) optical fiber, to the reflected and refracted light from conical surfaces. Broadly defined, “radial output” fibers produce a radial component if the term “radial” includes any off-axis emission (i.e. any fiber output other than a truly collimated output has a “radial” component or components).
Alternatively, “lateral emitting” fibers are typically limited to single- and multi-point off axis emissions. One example of lateral emitting fibers includes fibers with a series of notches on one side (FIG. 4). Another example includes fibers launching into stacked angular segments of fiber where the angles differ and begin at a critical angle for just a portion of the angular modes within the delivery fiber and progress to the critical angle as calculated for all angular modes carried within the fiber (FIG. 5).
A difference in philosophy exists within the art of the broadest surgical application of such fiber technology: varicose vein surgery or endovenous laser treatment (ELT). Laser energy is used to selectively damage vessels for post-surgical absorption. One camp advocates indirect heating of veins (via heating the blood within the vein, often to boiling) by firing laser energy into the blood-filled vessel while moving the fiber along the length of the segment under treatment. If the fiber is maintained within the center of the vessel, the radiant output of the fiber is relatively uniform and the speed of movement of the fiber is adjusted such as to account to variations in vessel diameter and shape, this technique is said to minimize complications of overtreatment such as vascular perforation but it does result in considerable thrombosis (blood clotting). Such treatment is generally affected with a simple high numerical aperture (NA) and flat polished fiber with some provision for preventing fiber tip to vessel wall contact.
Another camp advocates heating the vessel wall directly and avoids interactions with the blood to prevent post-operative complications from excessive thrombosis. It is with the latter camp that uniform and true radial emission is most beneficial as vessel perforations are more likely to result from irregular application of laser energy.
Numerous examples of radial and lateral emitting fibers have been attempted, these include: U.S. Pat. No. 4,669,467 (Willett, et al.) teaches stress-induced mode mixing for adjusting the light spot size and spot overlap of a plurality of fibers, terminated within a transparent protective capsule where the individual fibers may be arranged such as to point in slightly different directions, for the treatment of vascular tissue or obstructions thereof. The reference cites studies from the early 1980s where direct contact between optical fibers delivering laser energy within blood vessels and resulted in thrombosis and vascular perforation. A series of related works—U.S. Pat. No. 4,718,417 (Kittrell, et al.), U.S. Pat. No. 5,104,392 (Kittrell, et al.), U.S. Pat. No. 5,106,387 (Kittrell, et al.), U.S. Pat. No. 5,125,404 (Kittrell, et al.), U.S. Pat. No. 5,199,431 (Kittrell, et al.), U.S. Pat. No. 5,290,275 (Kittrell, et al.), U.S. Pat. No. 4,967,745 (Hayes, et al.), U.S. Pat. No. 5,192,278 (Hayes, et al.)—teach additional utility including spectroscopic diagnostics, dosage control via feedback during surgery, and alternative constructions, including use of additional optical elements within the protective capsule for altered illumination and collection patterns: a lens, a mirror, a holographic element, a prism, different lenses for individual fibers or groups of fibers and an acousto-optic deflector.
U.S. Pat. No. 4,842,390 (Sottini, et al.) discloses a fiber optic device for angioplasty (FIG. 1) that utilizes a protective microcapsule 5 about the fiber output 3, where the capsule 5 is shaped 6 so as to produce a diverging annular output, or hollow cone, where the distribution of laser energy is further controlled by shaping the plastic clad fiber 1, in the illustrated case, as a cone tip 3. Sottini included a capillary 8 within the invention, providing communication between the cap interior volume, through the adhesive seal to the outside for the purpose of venting “ . . . a dangerous pressure increase in the gas or air contained in the microcapsule” leading one to conclude that the efficiency of the radial emission was poor.
U.S. Pat. No. 5,093,877 (Aita, et al., FIG. 2) similarly teaches a protective cap 11 or capsule about a fiber 10 that serves as a beam conditioning ‘microlens’, where the closed end 16 of the transmissive capsule shapes the fiber output. Aita describes a gold or other radiopaque material ferrule 12 around the bare portion of the fiber 13, fixed in position with epoxy 18 and describes alternative curvatures for the first lens surface 15 and second lens surface 16 as well as filling the space 17 with materials of different refractive index for shaping the output from the flat fiber tip 14: one embodiment appearing virtually identical to '390 with a flat polished fiber. Filling the volume 17 with a fluid would produce a dangerous pressure increase, as described by Sottini, even at moderate laser powers unless the fluid were exceedingly transparent at the laser wavelength used and the device did not warm with use. Further, the ability of the second lens surface 16, or any optical surface in contact with whole or diluted blood, to refract the laser light emitted by the fiber tip 14 is greatly reduced because the refractive indices for whole blood (η=1.38) and dilute blood (η=1.35 @20%) are relatively similar to that of fused silica (η=1.46), particularly in comparison to air (η=1.00).
Similarly, U.S. Pat. No. 5,231,684 (Narciso, Jr., et al., FIG. 3) discloses a lens 20 mounted within the opening of the larger 21 of a pair of telescoping metal tubes 21 & 22 provided for redundant attachment to the optical fiber 23 buffer and cladding 24, where the space 29 between the lens curvature 25 and the fiber output 26 may be filled with fluid or elastomer having a similar refractive index as the fiber core and lens, thereby eliminating any refraction and therefore any function for the lens within the invention.
An abraded fiber core as a terminal diffusing segment of a surgical fiber is described in U.S. Pat. No. 5,019,075 (Spears, et. al.) teaches repair of physical damage to arterial walls during balloon angioplasty where light is intended to scatter in all directions along a length of the fiber that traverses the length of an angioplasty balloon along its axis.
U.S. Pat. No. 5,292,320 (Brown, et al.) teaches lateral delivery or side firing fibers (FIG. 4) where the single bevel tip 34 known to the art is augmented with a series of progressively shallower notches 33, 32 and 31 in the fiber 30, aligned substantially parallel to the primary bevel tip 34 plane, for redirecting fractions of the light within the fiber off the fiber axis and substantially in the same direction. Alternative embodiments include notches with differing angles as well as a spiral and other groove cut into a fiber for redirecting at least a portion of the energy carried therein. Brown teaches an optional protective cap 35 that is anything but optional. U.S. Pat. No. 5,496,308 (Brown, et al.) continues '320 where temperature dependent radiation form tissue is also collected in the device for monitoring and control.
An attempt to reduce Brown '320 to practice was made in 1994 by this inventor and Brown, but was promptly abandoned as impractical to manufacture and unsafe to use. An alternative design FIG. 5 was devised using angle polished segments of fiber 36, stacked within an elongated capsule 37 and butt-coupled to a flat polished 39 optical fiber 38 to produce a similar effect as sought in '320, but the distribution of the output energy profile proved difficult to control and the project was abandoned (non-patented work).
Similar to Aita '877, U.S. Pat. No. 5,342,355 (Long) teaches a transmissive cap for shaping the output of flat tip and convex tip optical fibers housed within the cap for heating tissue directly with laser light as refracted by the tip, heating the tip with laser light with the heat conducted to the tissue and exciting a gas trapped between the fiber output and the inside wall of the tip to form a plasma.
A system for treating prostate tissue with CO2 lasers via urethral access (FIG. 6) was described in U.S. Pat. No. 5,468,239 (Tanner) wherein a hollow waveguide 40 delivers energy across a space to a reflective cone 41 which redirects the radiation in 360° radial to the cone and orthogonal 43 to the waveguide longitudinal axis along which rays 42 are exclusively drawn.
U.S. Pat. No. 5,737,472 (Beranasson, et al.) teaches control of radial emission from a segment of fiber through differential defect generation in the fiber diameter, for example as produced by controlled sandblasting.
U.S. Pat. No. 5,908,415 (Sinofsky) teaches a transparent, plastic tube which surrounds and extends beyond the distal end of a fiber, where the tube is filled with a silicone matrix containing light-scattering particles uniformly distributed therein. A reflective surface at the distal end of the tube serves to plug the tube such that light traveling from the fiber to the distal end of the tube is reinforced by the light that is reflected back from the reflective surface to produce a comparatively uniform light intensity along the length of the tube. Such devices have found utility in photodynamic therapy and other applications where low laser power is sufficient.
U.S. Pat. No. 6,398,777 (Navarro, et al.) teaches intraluminal contact between a fiber optic tip and a blood vessel wall, using laser energy from 200 μm to 1100 μm, but does also mention that the tip of the fiber may be rounded.
A method similar to Sinofsky '415, with elements of Brown '320 and its offspring echoed therein, is taught in U.S. Pat. No. 6,893,432 (Intintoli), where a tube affixed to the end of a fiber houses stacked segments of differential mixtures of transmissive and dispersive compounds providing successive bands of radial emission that may be tuned by altering the mixtures housed in the tube segments.
U.S. Pat. Nos. 7,270,656; 8,211,095; and 8,851,080 (Gowda, et al.) teach active cooling of diffusive fiber tips for laser interstitial thermal therapy where the tips are produced by “embedded scattering centers” and less than full 360° emission is controlled by “reflective means”.
U.S. Pat. No. 7,273,478 (Appling) teaches away from radial emission for indirect heating of blood vessel walls via hot gas bubbles generated by axial output fibers, so long as those fiber tips are prevented from directly contacting the vessel wall by surrounding the fiber distal end with a ceramic spacer or, as described in U.S. Pat. No. 7,559,329 (Appling, et al.), an expandable spacer such as a wire basket.
U.S. Pat. No. 7,524,316 (Hennings, et al.) devotes a section to discussions of diffusing fiber tips stating therein, “The use of diffusing tip fibers for the treatment of varicose veins is unique and has not been previously described.” '316 further teaches that shaped fiber tips are largely useless in direct contact with blood due to closely matching refractive indices essentially eliminating non-standard refractive output, and teaches the use of an internally threaded (diffusing) material screwed onto the fiber buffer as a diffuser, a ceramic or other scattering material in the form of a bead placed in the fiber output path within a transparent protective capsule housing both fiber and bead, and simply housing a cone-tipped fiber within a protective capsule and a rounded tip (orb) fiber with no protective capsule. Such capped cone tip fibers are in common use today.
U.S. Pat. Appl. Pub. No. 2005/0015123 (Paithankar) teaches the use of diffusing tip fibers produced by a polymer or ceramic “cover” that includes a scattering material in the form of a cylinder about a fiber tip or a ball on the fiber tip to, “ . . . overcome the index of refraction matching properties of the optical fiber and the adjacent fluid or tissue.”
U.S. Pat. No. 7,386,203 (Maitland, et al.) describes diffuser tip fibers in considerable detail and modifies the prior art by employing a shape memory polymer as the medium for carrying the scattering centers for diffusion, purportedly providing some control of that diffusion by way of the shape memory polymer substrate.
A transparent spacer/nozzle serving as a coaxial coolant conduit is taught in U.S. Pat. No. 8,435,235 (Stevens) where the delivery fiber is recessed within the transparent spacer such that radiation is emitted through the spacer wall, through the nozzle opening or both as delivered by an axial fiber or cone-tipped fiber. The transparent spacer is prevented from contacting vessel walls in manners similar to '329. '235 also teaches a version of '239 (FIG. 7) where radial emission is accomplished via reflection from an inverted cone 45 placed distal to the axial output fiber 46, various means of centering the fiber assembly within vessel walls, a fiber assembly with an absorbing or scattering material placed within a fiber output path, a shaped tip fiber with an internal lumen for fluid conduction, etc.
In U.S. Pat. No. 8,257,347 (Neuberger, FIG. 8) a radially distributed beam is described where reflections in all directions orthogonal to the fiber longitudinal axis is accomplished by removing a portion of the fiber buffer 49 to expose the cladding 53 and removal of part of the fiber core 50 producing a short, cladding only section 54 of fiber that terminates in a conical void 52 within the solid core 50. The hollow, cladding only section 54 is then plugging at the opening with a short quartz cylinder 55, preserving an air pocket 51 for the low refractive index such that light imparting the conical void in the core is redirected laterally, in all directions. As the drawing within '347 depicting this embodiment intimates (FIG. 5 surface 52, in the original drawing, is sketched as rough and ragged), producing such a structure with smooth and flat surfaces (a right circular cone as opposed to curved surface cones akin to a Hershey's Kiss) for efficient reflection is a challenging proposition and requires exceptionally thick cladding 53 (sketched as thicker than the fiber core in the original figure within '347); anything less than a highly polished surface at 52 will result in significant scatter and axial emission. Cladding is expensive, particularly when it is fluorine-doped silica, as it must be for '347 to be produced.
U.S. Pat. No. 8,285,097 (Griffin) describes a strategy similar to '347 that is also impractical for ELA (Endoluminal Laser Ablation) also known as ELT (Endovenous Laser Treatment), EVLT (EndoVenous Laser Therapy, Angiodynamics) and other, similar acronyms. As shown in FIG. 9, a glass clad 62 tube 60, or annular core fiber, is gently collapsed over the length of the tube until the inner diameter ceases to exist 66, thus forming a solid core to annular core fiber adapter. The open end of the annular fiber is chamfered 70 to redirect energy laterally while the solid end 66 is spliced 68 to the end of a clad 74, solid core fiber 72. The entire bare glass section is secured within a protective cap 76. Light from the solid core fiber is gently redirected into the annular core about the vanishing conical bore 64, encounters the critical angle chamfer 70 and exits as radial emission centered approximately at twice the chamfer angle. In one embodiment, near orthogonal performance may be obtained with divergence lower than the solid core fiber to which the solid to annular core adapter was fused but axial transmission remains problematic due to the chamfer 70 failing to extend completely across the annular core 75.
U.S. Pat. No. 5,242,438 (Saadatmanesh, et al.) discloses a device that “ . . . includes special beam splitter or diverging device . . . a transmitting end portion which has a frustoconical, annular configuration defining an annular end surface for emitting the laser radiation in a generally ring-like, cylindrical beam which is generally parallel to the longitudinal axis . . . ” to avoid “ . . . exposing the tip of the conical reflecting surface to the laser energy, and the surface can still function to reflect the radiation generally laterally of the axis . . . ”. FIG. 10 illustrates this embodiment of the prior art where the “special beam splitter” 78 is analogous to the “solid core to annular adapter” in FIG. 9, but without the beam turning chamfer 70 at the terminal ID and instead relying upon the metallic reflector 82 distal to 78. It is of merit to note that the placement of the special beam splitter 78 between the fiber 80 output face 88 and the reflector 82 serves no real function other than the purported avoidance of exposing the tip of the conical reflecting surface 82 to the laser energy 84. As such, this embodiment serves only to permit imperfections in the reflecting cone and in the process generates Fresnel reflections within the device at 88 and 90.
Other embodiments in '438 are also directed to steering energy away from the center of terminal conical reflectors, including a concave conical pit in the fiber core akin to that in '347, produced with “a diamond drill” and a plurality of circumferentially disposed optical fibers or a ring output array. These strategies are necessary because directly illuminating a metallic conical reflector with the semi-Gaussian output profile of a laser driven optical fiber exposes the most difficult to prefect feature of the reflector, the cone point, to the highest energy densities. As with other prior art, overheating remains a central concern in '438 due to the inefficiencies of methods used for redirecting light therein.
U.S. Pat. No. 6,102,905 (Baxter, et al.) teaches a variety of embodiments of low power photodynamic therapy devices, similar to those taught by Sinofsky in '415, that must be low power due to the low temperature liability of the “optical elements” identified therein, include gradient index lenses, such as GRIN lenses (SELFOC®) produced by NSG America, made of gradient doped (germanium) silica, “cylindrical disks” and “hemispherical domes” made of PTFE, ETFE, FEP and PFA fluoropolymers, etc.
An inverted or opposing cone for reflecting the axial remnants from cone-tipped fibers is described in U.S. Pat. Appl. Pub. No. 2009/0240242 (Neuberger) along with a reprise of '320 and '308 where grooves are formed within the diameter of the fiber to produce a leakage pattern, a reprise of '347 where a hollow cone is machined in the end of an orb-tipped fiber, and combinations of hollow cones as well as auxiliary conical reflectors and simple axial output fibers protected by capsules or sleeves.
Generally addressing the deficiencies of cone-tipped optical fibers used in ELA treatment of varicose veins, including those housed within protective capsules, '242 teaches the addition of a secondary reflector 112 as depicted in FIG. 11. More completely, an optical fiber having a cladding 100 and a core 104 is equipped with a polished conical tip 110 where the angle of the cone is designed to reflect substantially all of the energy within the fiber core to angles significantly displaced from the fiber longitudinal axis. This does not occur for a simple cone tip fiber (FIG. 12) for a variety of reasons, one being imperfect cone tips 102 that allow emission of substantially axial radiation that, according to publication '242, will be intercepted and reflected by a second cone 112 made of quartz and sealed within the typical quartz protective capsule 106 found in much of the prior art.
U.S. Pat. Appl. Pub. No. 2010/0179525 (Neuberger) expands upon one embodiment within Pub. No. '242 and adds fiber centering mechanisms much like those disclose within Gowda, et al., and Appling. The single embodiment of Pub. No. '242 that appears to be expanded upon in the addition on FIG. 12 within Pub. No. '525 is not described within the text and is, as such, impossible to analyze. Notwithstanding this caveat, FIG. 12 in Pub. No. '242 appears to be a foreshortened version of one of the embodiments within prior art '097, where the protective cap 76 to FIG. 9 is replaced by a flat window about the chamfered opening 70.
U.S. Pat. Appl. Pub. No. 2011/0282330 (Harschack, et al.) teaches a variation of '320 and '308 where a series of grooves on one side of a fiber, or a spiral groove encircling the fiber, is/are replaced by what amounts to be circumferential grooves, described in Pub. No. '525 as “truncated cones”.
U.S. Pat. Appl. Pub. No. 2015/0057648 (Swift, et al.) teaches grooves and patterned grooves in a fiber for causing patterned leakage similar to the grooves in a sleeved and shaped fiber produced in our laboratory two decades ago and taught in U.S. Pat. No. 6,113,589 (Levy, et al.) for endometrial coagulation or ablation.